Open Discussion: Army Painting

With my latest project, I've decided to go all in and paint nearly the entire force at once.  It's a bold prospect that I'm sure the full ramifications won't be apparent until around 75% complete and I'm a jabbering mess curled up in a corner somewhere waiting to be carted off with a new comfy jacket that lets me hug myself.  But it's a leap I felt I had to make as all of my past projects seem to fall out of favor after just a few units are completed.

With my Grey Death space marines I didn't quite finish a single unit.  The Sons of Medusa found a much kinder fate but stalled out around 1500 points or so.  My Orks started life as an army quick paint but found no traction.  Eldar much the same fate as the orks. 

The time invested and set aside is also a major consideration this morning for me.  I'm finding I want to have the Space Wolves battle ready for the 22nd.  Dakkacon:  Philadelphia quickly approaches, and were I to have a completely new force for an event like that, it would be a major coupe against my horrendous case of modelers A.D.D. 

The question I present today is thus:  How do you approach an army paint?  Do you set a schedule?  Do you go all  in and paint it all at once?  Or are you a legacy painter, painting a unit or model at a time over the span of your hobby career?  How have you evolved over the years?